Questions tagged [linux]

A free and open source POSIX compatible operating system with a monolithic kernel and a kernel module system. Originally created by Linus Torvalds.

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51 views

Correct my understanding on a basic allocation memory

Here is the function If I understand correctly: There is a buffer of size 256 bytes created (malloc) in this buffer, the first 32 bits are set to 0 (because dword designates 32bits size) the next 32 ...
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1answer
79 views

ildasm on Linux: “original” ildasm.exe same as dotnet-ildasm?

I would like to use ildasm on Linux. The original one, that comes with the .NET SDK and can be found on Windows e.g. at c:\Program Files (x86)\Microsoft SDKs\Windows\v8.0A\bin\NETFX 4.0 Tools\. I ...
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1answer
123 views

Reverse getline(cin, text)

I'm trying to solve a crackme that was made in C++, and I was able to "recreate" a function call, through the library calls the program made. Here's the piece of code that I'm trying to reverse: ...
2
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1answer
79 views

Process Immediately Killed

I'm trying to reverse an ARM executable. It's for an embedded system, but I don't have any details about the normally targeted environment. Here's what file shows: ELF 32-bit LSB executable, ARM, ...
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2answers
314 views

Step Over not working in GDB

In the function below, let's say EIP is 0x400688. Now, I want to step over the call instead of stepping inside the subroutine. 0x40067a <main+4> sub $0x20,%rsp ...
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1answer
516 views

Radare2 webui - need help setting it up

How can you set up Radare2 webui in Kali or Ubuntu or any other OS? I've tried so many different methods but none of them have worked so far. I think both of them are debian based so that might be ...
2
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1answer
130 views

Determining an application's library call behaviour

I have a closed source Linux library libfoo that makes calls into another closed source library libbar for additional (mostly unneeded) features. However, I can't use libbar for ethical reasons, so I ...
2
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1answer
626 views

Custom gdb output

Yesterday i noticed a nice output from dbg while going through a write up on the internet. As am new to dbg i googled a lot as i wanted to make dbg work similar for me. As seen below this ...
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2answers
314 views

How can I pass input to my program while debugging it with IDA

I have a program that waits for the user to enter a string input, how can I enter that string input while debugging my program with IDA?
2
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1answer
258 views

Help needed to extract u-boot kernel & rootfs - nxp lpc 3143 processor

I have a board where in principle aim at emulating a DVD-ROM loading iso file from a drive. This board is running a ARM CPU with 32MB of ram and has no vga output. The firmware update comes with 2 ...
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1answer
909 views

extract zImage from MS-DOS executable

I have an aarch64 kernel image with the following magic number: root@localhost:/# cat msImage|xxd -l4 00000000: 4d5a 0091 MZ.. root@localhost:/# file msImage ...
2
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1answer
956 views

How can I view the dynamic symbol table of a running process?

For any dynamic executable on Linux there is a dynamic linker that stores the current symbol bindings somewhere. So when a new library is loaded it knows whether to bind the symbol or not. For ...
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2answers
2k views

Static analysis of Windows executable from a Linux platform

I am trying to do some static analysis on crackmes written for Windows on a Linux platform. I am using radare2. My problem is that most of the time I am unable to find the "real" code, for example the ...
2
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2answers
443 views

Putting an application in between client and server

I'm attempting to reverse engineer (without dissecting the source code, as my understanding is that reverse engineering by analyzing input and output and building something from scratch that fits is ...
2
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1answer
422 views

File Type - VCDIFF binary extract

I have a file I am trying to extract to view and I'm stuck... If I use binwalk I am able to get the gunzip file but unable to extract it... If I attempt to extract with gunzip I return the errors and ...
2
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1answer
2k views

gdb setting fs register on Linux

I'm debugging an ELF 64-bit binary using gdb and I notice that the %fs register is set to 0x63. For some testing that I'd like to perform I'd like to set the %fs register to 0x00. I tried doing a set ...
2
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1answer
553 views

Are there ANY supported Fermi Disassemblers out there?

I've recently started exploring the world of GPU-based malware. Academia doesn't have a ton of papers here, but there's some powerful ones. I'm looking at trying to improve the communities tools in ...
2
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1answer
44 views

IAT vs GOT address resolving: which of them resolve during runtime and which during load time by default?

So based on my knowledge on windows apps, as far as i know the IAT gets filled with correct addresses when the library gets loaded (correct me if I'm wrong) now in linux, they use GOT, and again ...
2
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1answer
106 views

ARM system crashes after changing stack address

-- Edit with latest update on the problem, it is not solved yet :( -- While playing with an ARM embedded Linux system (Version 3.8.13), out of curiosity, I created a small "debug" kernel module. ...
2
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1answer
1k views

Disassemblers resolving (ELF) section names

I'm working with linux executables and was just wondering how it is that section names are resolved to addresses upon disassembly of an ELF. For example take some random disassembly output from ...
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1answer
2k views

IDA Pro debugging: follow child process

I'm reverse engineering a malware that creates a number of child processes and I'm trying to do dynamic analysis of the ELF binary with IDA Pro and IDA's Local Linux Debugger, but I can't get IDA to ...
2
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1answer
420 views

How to store files on a router's NAND without writing the whole firmware

I want to modify my ZyXEL P-2812HNU-F1 dsl router by storing some extra files in /etc. However, /etc is mounted as tmpfs so changes are lost on reboot. But there's probably a way around it ;) # cat /...
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1answer
543 views

Writing own custome syscall/int 0x80 on x64 system

Is there a way to write my own syscall/int 0x80 without using them? So, normally it goes like setup registers ... syscall or int 0x80 and I am interested in doing this without syscall/int 0x80 ...
2
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1answer
282 views

Mechanisms to stop serial console accepting input on a Linux system?

I am working on a simple embedded system based around an Olinuxino board. This has a serial console header onboard. TX and RX are both connected to the respective pins on the microcontroller (i.e. ...
2
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1answer
245 views

How can I figure where my router stores it's configuration across reboots?

I'm currently researching my home router (D-Link 2760-U) which has a (kind-of) proprietary ISP firmware. What I'm trying to achieve is understanding how the router is persisting it's configuration ...
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0answers
35 views

submitting input into AFL fuzzer

I have some questions about the AFL Fuzzer: How does the AFL Fuzzer know where to inject the payload in the code I compile? For instance if I want to inject it in a specific parameter, how do I do it?...
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0answers
224 views

Extracting firmware image from binary

I have firmware file in .bin format, but I need get firmware.img image file and Kernel uImage file for reflashing bricked device. How can I get these parts? I used Binwalk to extract content, ...
2
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1answer
68 views

What is actually loaded here and different hexdump outputs on util-linux hexdump and on cutter and ghidra's hexdump

I was trying to understand what segment of file gets loaded by fourth LOAD header on phdr array. First 6 headers are shown below from readelf Program Headers: Type Offset ...
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0answers
2k views

OTOOL alternative for linux

I have a reverse engineering set up on a Mac machine. This set up does some reverse engineering on iOS applications(.ipa files). I'm migrating the setup from Mac to a linux machine. Currently on Mac, ...
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0answers
370 views

Obscure router refuses to flash OpenWrt

This is a very obscure Chinese router from a brand called Wavlink. It's the Model: WN529R2/WN529R2P. It's web interface was pretty limited and wouldn't allow firmware modifications. I found GND/Tx/Rx/...
2
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1answer
637 views

Is there a way to debug an elf file that runs with no problems with damaged header?

My question is general, but to have an example to work with, let us take one from Whirlwind Tutorial. ; tiny.asm BITS 32 org 0x00010000 db 0x7F, "ELF" ; ...
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0answers
2k views

How to decrypt the config.bin from ZTE ZXV10 H201L

I have this file from my router its backup of user config,I suppose its compresed with zlib and encrypted with AES. Utility which is resposible to compress it and encrypt it is called cspd. In side ...
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0answers
346 views

Using __kernel_vsyscall on x64 linux machine [closed]

I am trying to use __kernel_vsyscall instead of syscall/int 80 on linux x64. I have read that it can be done on Intel chips (I have one), but i can't find how can one do it. I have x32 version: int ...
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0answers
801 views

open a non-standard compression .tar.lzma file extracted from firmware download

We are trying to examine a firmware download for a product we have running on our local network. Using the command binwalk -Me filename we generated a folder that contains the following content: ...
2
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0answers
112 views

Trace replayer won't load binary debug information

So I'm debugging a linux application with what I believe DWARF debug information on x86-64 host. Everything is working fine and as expected - the source files are loaded immediately on function ...
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0answers
2k views

Knockoff CGA/EGA to vga firmware update [closed]

The problem with this, as I know from experience in dealing with this exact same issue is the firmware in the CGA/EGA/VGA converter board. There is an update that needs to be written to the converter ...
2
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0answers
261 views

Modern equivalent to rsymtab for reconstructing symbol table for statically linked / stripped binaries?

I'm working with a 32-bit ELF binary that (I believe) has been statically linked against a few different third-party libraries. It has also been stripped, so I don't have much to go on with respect to ...
2
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0answers
2k views

How to set-up GDB debugging in IDA Pro on Linux via Wine?

I tried running on linux via root terminal: gdbserver --multi localhost:23947 And then at IDA Pro at Wine I use Remote GDB debugger with my local ip and port: However when I start debugging I think ...
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0answers
167 views

How can one debug a program that can only be started by other processes?

I am now trying to figure out the innards of a custom made program that I've found difficult to debug using a debugger. The program starts by using a bash script wrapper to process input parameters, ...
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0answers
560 views

Flashing NVRAM with U-Boot 1.2.0

I tried to program SPI Flash NVRAM (S25FL064A) from U-boot, but it not allow to write: tftp 0x80000100 nvram.bin cp.b 0x80000100 0x007b0000 0x00050000 There is no error shown after cp.b command, ...
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2answers
1k views

USB programmer for SPANSION S25FL064P flash memory

Can someone recommend a handy inexpensive USB programmer for SPANSION S25FL064P flash memory?
2
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1answer
290 views

Cannot open '/proc/…/maps': No such file or directory in radare2 debug mode

When I try to load a program to radare2 debug mode, most of the time I get the following error: $sudo r2 -d a.out Hello world!= attach 2851 2851 Cannot open '/proc/2851/maps': No such file or ...
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2answers
2k views

How to locate module_init() offset from ELF header of Linux kernel module?

The header is self explanatory but to explain myself better. I have an ELF binary - loadable kernel module, compiled with symbols. I want to know how to locate the offset of the module_init() function....
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1answer
2k views

How does this version of `rm -rf /` work?

On this website, I found the following code: char esp[] __attribute__ ((section(”.text”))) /* e.s.p release */ = “\xeb\x3e\x5b\x31\xc0\x50\x54\x5a\x83\xec\x64\x68\" “\xff\xff\xff\xff\x68\xdf\xd0\xdf\...
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2answers
541 views

How can I change the a port a program listens on?

I want to change the port number a program listens on. The program is a proprietary linux binary, Plex, that always listens to tcp port 32400 (hard-coded). Since I want to run this on a shared server,...
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2answers
640 views

Is it possible copy and save bootloader using CLI telnet commands?

I need get copy of original Bootloader from device running embedded Linux. Is it possible copy and save bootloader using CLI telnet commands? I have full access to CLI interface. Is there way copy ...
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2answers
946 views

Modifying / Installing stock firmware on ISP Branded WRE2205

Our ISP, MWeb, gave us a free router and Wifi extender (WRE2205v2) as part of a new promotion. Neither of them really work at all (the extender works for about a minute then fails for no apparent ...
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2answers
1k views

Basic shellcode doesn't work when read from stdin

I am working on a basic shellcode that will spawn a shell after getting called in a 32-bit program. Here is the shellcode i'm using: xor %eax,%eax push %eax push $0x68732f2f push $...
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2answers
227 views

How to debug binary which doesn't have executable flags?

I'm trying to debug the binary which is not executable. As sample I'm using /bin/true with 644 permission: install -m 644 /bin/true . and I'm trying to run it as: $ lldb true (lldb) target create "...
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3answers
3k views

How does storing values in registers result in a functioning program? [closed]

I'm currently learning assembly, but I cannot seem to understand how storing values into registers and manipulating them results in a working program. I was wondering if you guys could provide a ...